The present invention relates to photocopying and more particularly to techniques by which to prevent object copyability by preventing the perception of object contrast by the image receptor.
There are situations where it is desired to render certain documents "copy secure". Of course, no precaution can absolutely prevent document copyability since an ordinary camera can copy anything that is visible. However, it is possible and sometimes desirable to add a degree of security to documents within a single organization by preventing their copyability by the particular photocopying apparatus in general use within that organization.
In other situations, it is sometimes desirable to render parts of documents uncopyable. An example of this exists right in the United States Patent and Trademark Office as well as in all other federal agencies. Under the Freedom of Information Act, government agencies including the Patent and Trademark Office are required to make their records available to public applicants except for such matters thereof "specifically exempted from disclosure by statute". The recent case of Irons v. Gottschalk 191 USPQ 481 relates to the application of this statute to the Patent and Trademark Office, and, citing Vaughn v. Rosen 484 F. 2d 820 (1973) specifically points up one problem of compliance. That is, in cases where government documents contain information which is within the mandate of the Freedom of Information Act as well as information which is exempted from disclosure under the Act, the problem of compliance becomes a problem of document masking or obliterating prior to making the same accessible. The techniques herein are directed toward such an application.
All photocopying processes include as one essential element the optical imaging of an object on a photoreceptor or image receptor. In turn, a prerequisite to recording of an image is the ability of the photoreceptor to perceive contrast in the object. Conversely, a prerequisite to image obliteration is the destruction of object contrast at the image receptor. Object contrast is a function of its color composition, and the spectral response of the optical system by which it is imaged. Spectral response is, in turn, a product of the spectral composition of the object illumination and the spectral sensitivity of the photoreceptor.
It is an object of this invention to provide the basis for techniques by which documents can be rendered copy secure as to one or more types of photocopying equipment.
Another object of this invention is to provide techniques for the simple and selective masking of documents for photocopying, for example in compliance with Freedom of Information Act requests.
Other objects, advantages, and features of this invention will become apparent from the following more detailed description thereof.